Wireless communication system and method for establishing a connection between user equipment and a mobility management entity thereof

ABSTRACT

The present invention relates to a wireless communication system and method for establishing connection between a User Equipment (UE) and a Mobility Management Entity (MME) in the wireless communication system in which the data-centric terminal requests the mobility management entity for attachment and checks, when the mobility management entity responds, data-centric features supported by the mobility management entity. According to the present invention, it is possible to connect the data-centric terminal to the mobility management entity supporting the data-centric features of the corresponding data-centric terminal efficiently in the wireless communication system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system andcommunication method thereof and, in particular, to a wirelesscommunication system and method for establishing connection between aUser Equipment (UE) and a Mobility Management Entity (MME) in thewireless communication system.

2. Description of the Related Art

Universal Mobile Telecommunications System (UMTS) is the thirdgeneration wireless communication system based on Global System forMobile communications (GSM) and General Packet Radio Services (GPRS) anduses Wideband Code Division Multiple Access (WCDMA). The 3^(rd)Generation Partnership Project (3GPP) as the UMTS standardizationorganization has proposed Evolved Packet System (EPS) such as Long TermEvolution (LTE). The LTE is a technology for implementing high speedpacket-based communication. An LTE system includes a Mobility ManagementEntity (MME) which manages the mobility of the User Equipment (UE)connected thereto.

DISCLOSURE OF INVENTION Technical Problem

However, as the services provided through the wireless communicationsystem are diversified, the UE is also being equipped varioussupplementary functions. The MME is embodied to support thesupplementary functions of the UE. Accordingly, in order to receive thecommunication service in association with a certain supplementaryfunction, the UE has to connect to the MME supporting the correspondingsupplementary function.

There is therefore a need of a method for connecting the UE to an MMEsupporting the intended supplementary function efficiently.

Solution to Problem

In accordance with an aspect of the present invention, a method forconnecting a data-centric terminal to a mobility management entity in awireless communication system includes requesting, at the data-centricterminal, the mobility management entity for attachment; and checking,when the mobility management entity responds, data-centric featuressupported by the mobility management entity.

Preferably, the method further includes determining, when the mobilitymanagement entity accepts the attachment, whether the data-centricterminal is to maintain the attachment to the mobility management entityaccording to the data-centric features; and performing, when thedata-centric terminal determines to maintain the attachment,data-centric communication with the mobility management entity using thedata-centric feature and, when not maintain the attachment, releasingthe attachment to the mobility management entity.

In accordance with another aspect of the present invention, a wirelesscommunication system includes a data-centric terminal for performingdata-centric communication using a unique data-centric feature; and amobility management entity for managing mobility of the data-centricterminal, wherein the mobility management entity notifies, when thedata-centric terminal requests for attachment, the data-centric terminalof data-centric features supported by the mobility management entity.

Preferably, the data-centric terminal determines, when the mobilitymanagement entity accepts the attachment, whether to maintain theattachment to the mobility management entity according to thedata-centric feature and performs, when the data-centric terminalsdetermines to maintain the attachment, data-centric communication withthe mobility management entity using the data-centric feature and,otherwise, releases the attachment to the mobility management entity.

Advantageous Effects

In order to solve the above problems, the wireless communication systemand method for establishing a connection between a UE and an MME in thesystem is capable of connecting the UE to the MME supporting thecorresponding supplementary function efficiently. That is, the presentinvention is capable of connecting a data-centric terminal to a mobilitymanagement entity supporting data-centric features efficiently.Accordingly, it is possible for the mobility management entitysupporting the data-centric feature to support the data-centriccommunication more efficiently and the data-centric terminal is capableof performing the data-centric communication more efficiently in thewireless communication system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the architecture of a wirelesscommunication system according to the first embodiment of the presentinvention,

FIG. 2 is a signal flow diagram illustrating the communication procedurein the wireless communication system according to the first embodimentof the present invention,

FIG. 3 is a signal flow diagram illustrating a connection procedure ofthe wireless communication system according to the first embodiment ofthe present invention,

FIG. 4 is a signal flow diagram illustrating the connection procedure ofthe wireless communication system according to the first embodiment ofthe present invention,

FIG. 5 is a flowchart illustrating the MME procedure in FIG. 3,

FIG. 6 is a flowchart illustrating the MME procedure in FIG. 4,

FIG. 7 is a flowchart illustrating the UE procedure in FIGS. 3 and 4,

FIG. 8 is a diagram illustrating the architecture of a wirelesscommunication system according to the second embodiment of the presentinvention,

FIG. 9 is a signal flow diagram illustrating the connection procedure inthe wireless communication system according to the second embodiment ofthe present invention,

FIG. 10 is a flowchart illustrating the operating procedure of the MMEin FIG. 9, and

FIG. 11 is a flowchart illustrating the operating procedure of the UE inFIG. 9.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention are described withreference to the accompanying drawings in detail. The same referencenumbers are used throughout the drawings to refer to the same or likeparts. Detailed description of well-known functions and structuresincorporated herein may be omitted to avoid obscuring the subject matterof the present invention.

FIG. 1 is a diagram illustrating the architecture of a wirelesscommunication system according to the first embodiment of the presentinvention.

Referring to FIG. 1, the wireless communication system of thisembodiment includes an enhanced Node B (eNB) 120, an MME 130, a HomeSubscriber Server (HSS), a Serving Gateway (S-GW) 150, and a Packet DataNetwork Gateway (P-GW) 160.

The UE 110 may be fixed or mobile. Also, the UE 110 may be a normal UEcapable of normal communication functions or a data-centric UE capableof specific supplementary function, e.g. data centric communicationfunction. Although the description is directed to the data-centric UEcapable of Machine Type Communication (MTC) function, the presentinvention is not limited thereto. Here, the MTC technology is applicableto Smart Metering for automated communication between a power companyserver and a home meter and an Alarm System for automated communicationbetween a security company server and an illegal home invasion alarm.

The eNB 120 controls a cell. The eNB 120 is a macro cell which is thecell of a normal cellular system. Here, the terms ‘eNB’ and ‘cell’ canbe used interchangeably. The eNB 120 establishes a connection with theUE 110 through a radio channel and controls radio resource. For example,the eNB 120 generates and broadcasts system information within the celland allocates to the UE 110 the radio resources for communicating packetdata or control information with the UE. 110. The system information mayinclude Public Land Mobile Network Identifier (PLMN ID) for access tothe PLMN via the eNB 120, eNB Cell Global ID (ECGI), and a Tracking AreaID (TAI) of the tracking area including the cell. The eNB 120 makes ahandover decision and commands handover based on the channel measurementresult of the current cell and neighbor cells that is fed back by UE110. In order to accomplish this, the eNB 120 is provided with a controlprotocol such as Radio Resource Control Protocol related to radioresource management.

The MME 130 manages the UE 110 in idle mode and selects the S-GW 150 andP-GW 160 for the UE 110. The MME is also responsible for roaming andauthentication-related functions. The MME 130 is also processing thebearer signal generated by the UE 110. For this purpose, the MME 130allocates identity information to the UE 110 and manages the UE 110attached with the identity information. Here, the MME 130 can be anormal MME for supporting the normal UEs or the data-centric MME forsupporting the data-centric UE. Although the description is directed tothe MTC MME for supporting the MTC UE, the present invention is notlimited thereto.

The MME is connected to the eNB 120 through a radio channel and to theUE 110 via the eNB 120. The MME 130 is connected to the eNB 120 throughan S1-MME interface. At this time, the MME 130 communicates with the UE110 using Non Access Stratum (NAS) messages. The MME 130 supports aplurality of tracking areas to connect to a plurality of eNBs 120 usingthe corresponding tracking area information. That is, the eNBs using thesame tracking area information can connect to the same MME 130. The eNBsusing different tracking area informations can connect to different MMEs130. The eNBs using the different tracking area informations may connectto the same MME 130.

In order to support the data-centric communication efficiently in thewireless communication system, various data-centric proprieties shouldbe defined. For example, the MTC feature for supporting the MTCtechnology efficiently in the wireless communication system may be LowMobility, Time Controlled, Time Tolerant, Packet Switched Only (PSOnly), Small Data Transmissions, Mobile Originated Only, InfrequentMobile Terminated, Secure Connection, Location Specific Trigger, NetworkProvided Destination for Uplink Data, Infrequent Transmission, or GroupBased MTC.

For the MTC UE and MTC MME, some of the MTC features are mandatory andothers are optional. For example, in the smart metering for the MTC UEto report utilization amount measured for a predetermined durationperiodically, the MTC UE transmits the data less than a few hundredbytes, the ‘Small Data Transmissions’ feature is mandatory. In thiscase, the ‘Location Specific Trigger’ feature for the MTC UE to initiateMTC at a specific position may not be mandatory between the MTC UE andthe MTC MME. In order to perform MTC efficiently, the MTC UE has toattach the MTC MME supporting the required MTC features.

In the following description, the term ‘essential MTC feature’ denotesthe MTC feature required mandatorily for the MTC UE to perform MTC. Thatis, if an essential MTC feature is supported by a radio network, the MTCUE is capable of performing MTC via the MTC MME of the radio network.The term ‘optional MTC feature’ denotes the MTC feature which is notrequired mandatorily for the MTC UE to perform MTC. The optional MTCfeature may be required for MTC optimization in the radio network. Thatis, although the radio network does not support the optional MTCfeatures, the MTC UE is capable of MTC via the MTC MME of the radionetwork.

In the following description, the term ‘supported MTC feature’ denotesthe MTC feature supported by the MTC MME of the wireless communicationin order for the MTC UE to perform MTC. At this time, the supported MTCfeature can be configured so as to be included in the essential MTCfeatures of the MTC UE or not. The supported MTC feature also can beconfigured so as to be included in the optional MTC features of the MTCUE or not.

That is, if the supported MTC feature is included in the essentialfeatures, the MTC MME is capable of supporting the MTC UE. The MTC UE iscapable of performing MTC vial the MTC MME using the essential MTCfeature. At this time, if the supported MTC feature includes an optionalMTC feature, the MTC UE is also capable of using the optional MTCfeature in performing MTC. If the supported MTC feature does not includeany essential MTC feature, the MTC MME cannot support the MTC of the MTCUE. That is, the MTC UE cannot perform MTC via the MTC MME. Here,although the supported MTC feature includes an optional MTC feature, theMTC UE cannot perform MTC via the MTC MME. According, in order for theMTC UE to perform MTC via the MTC MME, the MTC UE should attach the MTCMME supporting the essential MTC feature.

The HSS 150 stores the subscription data of the UE 110. If the UEattaches to the MME 130, the HSS 140 updates the subscriptioninformation of the UE 110. The HSS 140 provides the MME 130 with thesubscription information of the UE 110 in order for the MME 130 tocontrol the UE 110 with the subscription information. The subscriptioninformation may include the MTC subscription information for an MTC UE.Here, the MTC subscription information may include the essential andoptional MTC features of the corresponding MTC UE.

The S-GW 150 connects to the eNB 120 and the MME 130 through radiochannels. The S-GW 150 connects to the eNB through an S1-U interface.The S-GW 150 is responsible for the mobility control function of the UE110. When the UE performs handover between the eNBs 120 or between 3GPPradio networks, the S-GW 150 works as a mobility anchor of the UE 110.

The P-GW 160 is connected to the S-GW 150 through a radio channel. Here,the P-GW 160 is connected to the S-GW through a S5 interface. The P-GW160 connects to the Internet Protocol (IP) network 170. The P-GW 160 isresponsible for the IP address allocation function and packetdata-related function. That is, the P-GW 160 delivers the packet datafrom the IP network 170 to the UE 110 via the S-GW 150 and eNB 120. Whenthe UE 110 roams between the 3GPP radio network and non-3GPP radionetwork, the P-GW 160 works as the mobility anchor of the UE 110. TheP-GW 160 also determines the bearer band for the UE 110 and performspacket data forwarding and routing function.

If it connects to the eNB 120 of the wireless communication system, theUE 110 is capable of being connected to the IP network 170 through thedata path via the eNB 120, S-GW 170, and P-GW 160 so as to communicatepacket data. The UE 110 is capable of transmitting a NAS request messageto the MME 130 via the eNB 120. At this time, the NAS request messagemay include at least one of an attach request, tracking area updaterequest, or service request. Upon receipt of the NAS request message,the eNB selects the MME 130 according to a Network Node SelectionFunction (NNSF) to deliver the NAS request message to deliver the NASrequest message. This is because the eNB 120 may be connected to pluralMMEs 130 through separate S1-MME interfaces.

Although the description is directed to the case where the UE 110 is anMTC UE and the eNB 120 is connected to a normal MME and an MTC MMEthrough separate S1-MME interfaces in this embodiment, the presentinvention is not limited thereto. That is, although the MTC UE isreplaced with another UE implemented to perform a specific supplementaryfunction and differentiated from the normal UE and the MTC MME withanother MME supporting the another UE, the present invention can beapplied. In this embodiment, the description is made under theassumption that the MTC MME determines whether to accept attachment ofthe MTC UE according to whether the MTC MME support the essential MTCfeature of the MTC UE. That is, the description is made under theassumption that all other conditions for determining whether to acceptattachment of the MTC UE in the normal MME or the MME are fulfilled.

FIG. 2 is a signal flow diagram illustrating the communication procedurein the wireless communication system according to the first embodimentof the present invention.

Referring to FIG. 2, in the communication procedure of the wirelesscommunication system of this embodiment, the MTC UE 111 first requeststhe MME 130 for attach via the eNB 120 at step 201. At this time, theMTC UE 111 retains the essential and optional MTC features. That is, theMTC UE 111 selects one of the radio networks accessible through the eNB120 and requests for the attachment to the MME 130 of the correspondingradio network. Here, the MTC UE 111 is capable of storing theinformation on the access PLMNs. At this time, the MTC UE 111 is capableof requesting for the attachment to the MTC MME 131 or the normal MME(as denoted by reference number 133 of FIG. 3). The MTC UE 1110 iscapable of transmitting International Mobile Subscriber Identity (IMSI)to the MME 130.

Next, if the MTC UE 111 requests for attachment, the MME 130 notifiesthe MTC UE 111 of the MTC features via the eNB 120. At this time, theMME 130 retains the supported MTC feature supportable by thecorresponding radio network. The MME 130 notifies the MTC UE 111 of thesupported MTC feature. Here, the MME 130 expresses the supported MTCfeatures in a bitmap for notifying of the MTC features and transmits thebitmap to the MTC UE 111. With the bitmap, the MTC UE 111 is capable ofchecking whether the MME 130 supports MTC. The MTC UE is also capablefor checking whether the MME 130 supports the essential MTC feature oroptional MTC feature. That is, the MTC UE 111 is capable of identifyingthe MTC features supported by the MME 130 or not.

FIG. 3 is a signal flow diagram illustrating a connection procedure ofthe wireless communication system according to the first embodiment ofthe present invention.

Referring to FIG. 3, in the connection procedure of the wirelesscommunication system according to this embodiment, the MTC UE 111requests the MME 130 for attachment via the eNB 120 at step 211. At thistime, the MTC UE 111 is retaining the essential and optional MTCfeatures. That is, the MTC UE 111 selects one of the radio networksaccessible with the eNB 120 and requests for attachment to the MME 130of the corresponding radio network. Here, the MTC UE 111 is capable ofretaining the information on the PLMNs accessible through the eNB 120.At this time, the MTC UE 111 is capable of attachment to the MTC MME 131or the normal MME (denoted by reference number 133 of FIG. 3). The MTCUE 111 is capable of transmitting the unique subscription identityinformation to the MME 130.

Next, if the MTC UE 111 requests for attachment, the MTC MME 131requests the HSS 140 for the subscription information of the MTC UE 111at step 213. At this time, the MTC MME 131 reports the location of theMTC UE 111 to the HSS 140 to request for the subscription information ofthe MTC UE 111. Here, the MTC MME 131 sends the subscription identityinformation of the MTC UE 111. Afterward, if the subscriptioninformation of the MTC UE 111 is requested, the HSS 140 responds bysending the subscription information of the MTC UE 111 to the MTC MME131. At this time, the HSS 140 updates the location of the MTC UE 111and notifies the MTC MME 131 of the update to transmit the subscriptioninformation of the MTC UE 111. That is, the HSS 140 retrieves thesubscription information of the MTC UE 111 using the subscriptionidentity information and transmits the found subscription information tothe MTC MME 131. At this time, the subscription information includes theMTC subscription information of the MTC UE 111. The MTC subscriptioninformation includes the essential and optional MTC features of the MTCUE 111.

If the subscription information of the MTC UE 111 is received, the MTCMME 131 analyzes the subscription information to determine whether it ispossible to support the essential MTC feature of the MTC UE 111 at step217. At this time, the MTC MME 131 is retaining the MTC featuressupportable by the corresponding radio network. That is, the MTC MME 131checks the essential MTC feature in the subscription information of theMTC UE 111 to determine whether the essential MTC feature is included inthe supported MTC features. Here, if the supported MTC features includethe essential MTC feature of the MTC UE 111, the MTC MME 131 determinesthat the essential MTC feature of the MTC UE 111 is supportable.Otherwise, if the supported MTC features do not include the essentialMTC feature of the MTC UE, the MTC MME 131 determines that the essentialMTC feature of the MTC UE 111 is not supportable.

If it is determined that the essential MTC feature of the MTC UE 111 issupportable, the MTC MME 131 accepts the registration of the MTC UE 111at step 219. At this time, the MTC MME 131 notifies the MTC UE 111 ofthe supported MTC features. Here, the MTC MME 131 expresses thesupported MTC features in a bitmap for notifying of the MTC features andtransmits the bitmap to the MTC UE 111.

The attachment to the MME 130 is accepted, the MTC UE 111 determineswhether the MME 130 supports MTC at step 221. That is, the MTC UE 111determines whether the MME 130 is the MTC MME 131. The MTC UE 111determines whether the MME 130 is the MTC MME 131 based on whether theMME 130 has transmitted the MTC features. If it is determined that theMTC features has been transmitted by the MME 130, the MTC UE 111determines that the MME 130 is the MTC MME 131. Otherwise, if it isdetermined that the MTC features has not been transmitted by the MME130, the MTC UE 1111 determines that the MME 130 is the normal MME 133.Afterward, the MTC UE 111 performs MTC through the MTC MME 131 at step223. At this time, the MTC UE 111 is capable of performing MTC using theessential MTC feature. The MTC UE 111 is also capable of performing MTCusing the supported MTC features of the MTC MME 131. That is, the MTC UE111 is capable of checking the MTC feature selected among the supportedMTC features for use in performing MTC.

If it is determined that the essential MTC feature of the MTC UE 111 isnot supportable at step 217, the MTC MME 131 rejects the registration ofthe MTC UE 111 at step 227. At this time, the MTC MME 131 notifies theMTC UE 111 of the supported MTC features. Here, the MTC MME 131expresses the supported MTC features in a bitmap for notifying of theMTC features and transmits the bitmap to the MTC UE 111. In this way,the MTC UE 111 is capable of checks the MTC features not supported bythe MTC MME 131. The MME 131 is also capable of notifying the MTC UE 111of the cause of the registration rejection. That is, the MTC MME 131 iscapable of notifying the MTC UE 111 that the essential MTC feature isnot supported. The MTC MME 131 is also capable of notifying the MTC UE111 of a retrial period for attachment. The MTC MME 131 is also capableof notifying the MTC UE 111 of the information on PLMNs for retrial ofregistration.

FIG. 4 is a signal flow diagram illustrating the connection procedure ofthe wireless communication system according to the first embodiment ofthe present invention.

Referring to FIG. 4, in the connection procedure of the wirelesscommunication system of this embodiment, the MTC UE 111 first requeststhe MME 130 for attachment via the eNB 120 at step 311. At this time,the MTC UE 111 is retaining the essential and optional MTC features.That is, the MTC UE 111 selects one of the radio networks accessiblethrough the eNB 120 to requests the MME 130 of the corresponding radionetwork for attachment. Here, the MTC UE 111 is capable of retaining theinformation on the PLMNs accessible through the eNB 120. At this time,the MTC UE 111 is capable of requesting the MTC MME 131 or the normalMME 133 for attachment. The MTC UE 111 is capable of transmitting theunique subscription identity information to the MME 130.

Upon receipt of the registration request from the MTC UE 111, the normalMME 133 requests the HSS 140 for the subscription information of the MTCUE 111 at step 313. At this time, the normal MME 133 is capable ofreporting the location of the MTC UE 111 to request for the subscriptioninformation of the MTC UE 111. Here, the normal MME 133 delivers thesubscription identity information of the MTC UE 111 to the HSS 140.Afterward, if the subscription information of the MTC UE 111 isrequested, the HSS 140 responds with by transmitting the subscriptioninformation of the MTC 111 to the normal MME 133. At this time, the HSS140 updates the location of the MTC UE 111 and notifies the normal MME133 of the update to transmit the subscription information of the MTC UE111. That is, the HSS 140 retrieves the subscription information of theMTC UE 111 using the subscription identity information and transmits thefound subscription information to the normal MME 133. At this time, thesubscription information includes the MTC subscription information forthe MTC UE 111. Here, the MTC subscription information includes theessential and optional MTC features of the corresponding MTC UE 111.

If the subscription information of the MTC UE 111 is received, thenormal MME 133 accepts the registration of the MTC UE 111 at step 317.At this time, the normal MME 133 is not capable of processing the MTCsubscription information in the subscription information of the MTC UE111. That is, the normal MME 133 cannot discriminate between the MTC UE111 and normal UE (not shown). As a consequence, the normal MME 133regards the MTC UE 111 as a normal UE so as to accept the registrationof the MTC UE 111.

If the registration is accepted by the MME 130, the MTC UE 111determines whether the MME 130 supports MTC at step 319. That is, theMTC UE 111 determines whether the MME 130 is the MTC MME 131. At this,the MTC UE 111 is capable of determining whether the MME 130 is the MTCMME 131 according to whether the MME 130 has notified of the MTCfeatures. If the MTC features have been notified, the MTC UE 111determines whether the MME 130 is the MTC MME 131. Otherwise, if no MTCfeature has been notified, the MTC UE 111 determines that the MME 130 isthe normal MME 133. The MTC UE 111 also detaches from the normal MME 133at step 321. That is, since the normal 133 cannot support the essentialMTC feature, the MTC UE 111 detaches from the normal MME 133.

Although, in this embodiment, the description is directed to theexemplary case where the MTC UE 111 determines whether the MME 130 hasreported the MTC features to determine whether the MME 130 is the MTCMME 131, the present invention is not limited thereto. That is, thepresent invention can be implemented in such a way that the MTC UE 111discriminates between the MTC and normal MMEs 131 and 133 based on theMTC features transmitted by both the MTC and nor MME 131 and 133. Thatis, the MTC MME 131 is retaining the supported MTC features and thenormal MME 133 is not retaining the supported MTC features. If the MTCUE 111 requests for attachment, the MTC MME 131 expresses the supportedMTC features in a bitmap for notifying of the MTC features and transmitsthe bitmap to the MTC UE 111. Meanwhile, if the MTC UE 111 request forattachment, the normal MME 133 expresses the supported MTC features in abitmap for notifying of the MTC features and transmits the bitmap to theMTC UE 111. Here, the normal MME 133 transmits the bitmap indicatingthat there is no supported MTC feature.

In order to accomplish this, the MTC UE 111 is capable of determiningwhether the MME 130 supports MTC. Also, the MTC UE 111 is capable ofdetermining whether the MME 130 supports the essential MTC feature oroptional MTC feature. That is, the MTC UE 111 is capable ofdiscriminating between the MTC features supported by the MME 130 and theMTC features not supported by the MME 130.

FIG. 5 is a flowchart illustrating the MME procedure in FIG. 3. Here,the description is made under the assumption that the MME is an MTC MME.

Referring to FIG. 5, in the procedure according to this embodiment, theMTC MME 131 first detects the attach request of the MTC UE 111 at step411. At this time, the MTC MME 131 checks the subscription identityinformation of the MTC UE 111. The MTC MME 131 requests the HSS 140 forthe subscription information of the MTC UE 111 at step 413. At thistime, the MTC MME 131 reports the location of the MTC UE 111 to the HSS140 to request for the subscription information of the MTC UE 111. Here,the MTC MME 131 sends the subscription identity information of the MTCUE 111 to the HSS 140.

Subsequently, if the subscription information of the MTC UE 111 isreceived from the HSS 140, the MTC MME 131 detects this at step 415 andanalyzes the subscription information to determine whether it cansupport the essential MTC feature at step 417. At this time, the MTC MME131 is retaining the supported MTC features supportable in thecorresponding radio network. That is, the MTC MME 131 checks theessential MTC feature in the subscription information of the MTC UE 111to determine whether the essential MTC feature is included in thesupported MTC feature. If the essential MTC feature of the MTC UE 111 isincluded in the supported MTC features, the MTC MME 131 determines thatit is possible to support the essential MTC feature of the MTC UE 111.Otherwise, if the essential MTC feature of the MTC UE 131 is notincluded in the supported MTC features, the MTC MME 131 determines thatit is impossible to support the essential MTC feature of the MTC UE 111.

Finally, if it is determined that it can support the essential MTCfeature of the MTC UE 111, the MTC MME 131 accepts the attachment of theMTC UE 111 at step 419. At this time, the MTC MME 131 notifies the MTCUE 111 of the supported MTC features. Here, the MTC MME 131 expressesthe supported MTC features in a bitmap for notifying of the MTC featuresand transmits the bitmap to the MTC UE 111. The MTC MME 131 performs MTCwith the MTC UE 111 at step 421. At this time, the MTC MME 131 iscapable of performing the MTC with the essential MTC feature for the MTCUE 111. The MTC MME 131 is also capable of performing the MTC with thesupported MTC features for the MTC UE 111. That is, in order to optimizethe MTC, the MTC MME 131 is capable of checking MTC feature selected forthe MTC UE 111 among the supported MTC features.

If it is determine that it cannot support the essential MTC feature ofthe MTC UE 111 at step 417, the MTC MME 131 rejects the attachment ofthe MTC UE 111 at step 427. At this time, the MTC MME 131 notifies theMTC UE 111 of the supported MTC features. The MTC MME expresses thesupported MTC features in a bitmap for notifying of the MTC features andtransmits the bitmap to the MTC UE 111. In this way, the MTC UE 111 iscapable of checking the MTC feature not supported by the MTC MME 131.The MTC MME 131 is also capable of notifying of the reason of theattachment rejection. That is, the MTC MME 131 is capable of notifyingthe MTC UE 111 that it does not support the essential MTC function. TheMTC MME 131 is also capable of notifying the MTC UE 111 of the retrialperiod for attachment. The MTC MME 131 is also capable of notifying ofthe information on different PLMNs for use in retrial of attachment.

FIG. 6 is a flowchart illustrating the MME procedure in FIG. 4. Here,the description is made under the assumption that the MME is a normalMME.

Referring to FIG. 6, in the MME procedure of the embodiment, the normalMME 133 firsts detects the attach request of the MTC UE 111 at step 511.At this time, the normal MME 133 checks the subscription identityinformation of the MTC UE 111. The normal MME 133 requests the HSS 140for the subscription information of the MTC UE 111 at step 513. At thistime, the normal MME 133 reports the location of the MTC UE 111 to theHSS 140 to request for the subscription information of the MTC UE 111.Here, the normal MME 131 transmits the subscription identity informationof the MTC UE 111 to the HSS 140.

Finally, if the subscription information of the MTC UE 111 is receivedfrom the HSS 140, the normal MME 133 detects this at step 515 andaccepts the attachment of the MTC UE 111 at step 517. At this time, thenormal MME 133 does not process the MTC subscription information in thesubscription information of the MTC UE 111. That is, the normal MME 133does not discriminate between the MTC UE 111 and the normal UEs. As aconsequence, the normal MME 133 regards the MTC UE 111 as a normal UE soas to accept attachment of the MTC UE 111. Here, the normal MME 133expresses the supported MTC features in a bitmap for notifying of theMTC features and transmits the bitmap to the MTC UE 111. That is, thenormal MME 133 is capable of transmitting the bitmap configured toindicate that there is not supported MTC feature. Afterward, the normalMME 133 releases the attachment of the MTC UE 111 at step 519. At thistime, the normal MME 133 releases the attachment according to therequest from the MTC UE 111. That is, since it cannot support theessential MTC feature, the normal MME 133 releases the attachment of theMTC UE 111.

FIG. 7 is a flowchart illustrating the UE procedure in FIGS. 3 and 4.Here, the description is made under the assumption that the UE is an MTCUE.

Referring to FIG. 7, in the UE procedure of this embodiment, the MTC UE111 first selects the MME 130 at step 611. That is, the MTC UE 111selects one of the radio networks accessible through the eNB 120. Atthis time, the MTC UE 111 is capable of retaining the information on theoperators of the radio networks accessible through the eNB 120. The MTCUE 111 is retaining the essential MTC feature and selected MTC feature.Afterward, the MTC UE 111 requests the MME 130 for attachment at step613. At this time, the MTC UE 111 is capable of requesting the MTC MME131 or the normal MME 133 for the attachment. The MTC UE 111 is alsocapable of transmitting the unique subscription identity information tothe MME 130.

Subsequently, if the MME 130 accepts the attachment, the MTC UE 111detects this at step 615 and determines whether the MME 130 supports MTCat step 617. At this time, the MTC UE 111 is capable of determiningwhether the MME 130 is an MTC MME 131 according to whether the MTCfeatures have been reported by the MME 130. If the MTC features havebeen reported by the MME 130, the MTC UE 111 determines that the MME 130is the MTC MME 131. If the MTC features have not been reported, the MTCUE 111 determines that the MME 130 is the normal MME 133. Meanwhile, ifthe bitmap indicating the MTC features is received from the MME 130, theMTC UE 111 is capable of checking the supported MTC features of the MME130. The MTC UE 111 is also capable of determining whether the MME 130supports the MTC for the MTC UE 111 according to the supported MTCfeatures of the MME 130.

Finally, if it is determined that the MME 130 supports MTC at step 617,the MTC UE 111 performs MTC through the MME 130, i.e. the MTC MME 131.At this time, the MTC MME 111 is capable of performing MTC using theessential MTC feature. The MTC UE 111 is also capable of performing MTCusing the supported MTC features of the MTC MME 131. That is, the MTC UE111 is capable of checking the MTC feature selected among the supportedMTC features of the MTC MME 131 for use in performing MTC.

Otherwise, if it is determined that the MME 130 does not support MTC atstep 617, the MTC UE 111 detaches from the MME 130 at step 627. That is,since the normal MME 133 cannot support the essential MTC feature, theMTC UE 111 releases the attachment to normal MME 133. At this time, theMTC UE 111 is capable of storing the operator information of the radionetwork corresponding to the normal MME 133 to reference in selectingthe MME 130 afterward. That is, the MTC UE 111 is capable of storing theoperator information of the corresponding radio network as forbiddenPLMN ID to avoid attachment to the corresponding normal MME 133afterward.

Meanwhile, if the attachment to the MME 130 is rejected at step 615, theMTC UE 111 detects this at step 635 and waits for the attachment retrialperiod at step 637. At this time, the MTC UE 111 is capable of receivingthe bitmap informing of the MTC features from the MME 130 and checks theMTC features that are not supported by the MME 130. The MTC UE 111 iscapable of waiting for a predetermined attachment retrial period. TheMTC UE 111 is also capable of waiting for the attachment retrial periodas notified by the MME 130. Afterward, the MTC UE 111 reselects the MME130 at step 639 and returns the procedure to step 615. The MTC UE 111performs at least a part of steps 615 to 639 again.

At this time, the MTC UE 111 is capable of retaining the operatorinformation of the radio networks, which the eNB 120 is accessible, foruse in selecting another MME 130. The MTC UE 111 is also capable ofusing the operation information of the different radio networks that arereported by the MTC MME 131 for selecting another MME 130. For example,if the operation informations of the individual radio networks arestored, the MTC UE 111 selects another MME using the information and,otherwise, selects another MME 130 as notified by the MTC MME 131. Here,the MTC UE 111 is capable of selecting another MME 130 by referencingpreviously stored access-forbidden information. That is, the MTC UE iscapable of another MME 130 after ruling out the selection-forbiddeninformation in the operator informations of other radio networks thatare stored previously or notified by the MTC MME 131.

According to this embodiment, it is possible to connect the UE 110 tothe MME 130 supporting the intended supplementary function efficientlyin the wireless communication system. That is, it is possible to connectthe MTC UE 111 to the MTC MME 131 supporting the essential MTC feature.Accordingly, the MTC MME 131 is capable of supporting MTC moreefficiently, and the MTC UE 111 is capable of performing MTC moreefficiently in the wireless communication system.

Although the above-description is directed to the exemplary case fordetermining whether to accept the attachment of the MTC UE according towhether the MTC MME supports the essential MTC feature, the presentinvention is not limited thereto. That is, the present invention can beimplemented in such a way that the MTC UE determines whether the MTC MMEsupports the essential MTC feature. At this time, criterion fordetermining whether to maintain the attachment of the MTC UE to the MTCMME can be configured by an external server.

FIG. 8 is a diagram illustrating the architecture of a wirelesscommunication system according to the second embodiment of the presentinvention.

Referring to FIG. 8, the wireless communication system of thisembodiment includes a policy server 700, a UE 710, an eNB 720, an MME730, an HSS, an S-GW 750, and a P-GW 760. In the wireless communicationof this embodiment, since the configurations and functions of the UE710, the eNB 720, the MME 730, the HSS 740, the S-GW 750, and the P-GW760 are similar to those described in the previous embodiment, detaileddescription thereof are omitted herein.

The policy server 700 determines the MTC policy per MTC UE for use inassociation with the UE 710. At this time, the policy server 700 sendsthe MTC policy to the MTC UE via the eNB 720 in order for the MTC UE toconfigure the MTC policy. Here, the MTC policy includes the essentialMTC features for the MTC UE, selected MTC features, and information onwhether it is possible to maintain the attachment to the radio networksupporting no essential MTC features of the MTC UE. The policy server700 can be an Open Mobile Alliance-Device Management (OMA-DM) server.

FIG. 9 is a signal flow diagram illustrating the connection procedure inthe wireless communication system according to the second embodiment ofthe present invention. Although the MTC UE is communicating with theserver or the MTC MME via an eNB, this is omitted herein.

Referring to FIG. 9, in the connection procedure of the wirelesscommunication system of this embodiment, the policy server 700 firstconfigures the MTC policy for the MTC UE 711 at step 811. At this time,the MTC policy includes the essential MTC features, the selected MTCfeatures, and information on whether the MTC UE 711 may maintain theattachment to the radio network which does not support the essential MTCfeatures. Afterward, the MTC UE 711 requests the MME 730 for attachmentat step 813. That is, the MTC UE 711 selects one of the radio networksaccessible via the eNB 720 and request the MME 730 of the correspondingradio network for attachment. Here, the MTC UE 711 is capable ofretaining the operator informations of the radio networks accessible viathe eNB 720. At this time, the MTC UE 711 is capable of requesting theMTC MME 731 or a normal MME (not shown) for attachment. The MTC UE 711is also capable of transmitting unique subscription identity informationto the MME 730.

If the MTC UE 711 requests for attachment, the MTC MME 731 requests theHSS 740 for the subscription information of the MTC UE 711 at step 815.At this time, the MTC MME 7312 reports the location of the MTC UE 711 tothe HSS 740 to request for the subscription information of the MTC UE711. Here, the MTC MME 731 delivers the subscription identityinformation of the MTC UE 711 to the HSS 740. Afterward, if thesubscription information of the MTC UE 711 is requested, the HSS 740responds by sending the subscription information of the MTC UE 711 tothe MTC MME 731 at step 817. At this time, the HSS 740 updates thelocation of the MTC UE 711 and notifies the MTC MME 731 of the updatewith the subscription information of the MTC UE 711. That is, the HSS740 retrieves the subscription information of the MTC UE 711 in matchwith the subscription identity information and sends the foundsubscription information to the MTC MME 731. At this time, thesubscription information includes the MTC subscription information forthe MTC UE 711. Here, the MTC subscription information includes theessential MTC features and the selected MTC feature of the correspondingMTC UE 711.

If the subscription information of the MTC UE 711 is received, the MTCMME 731 accepts the attachment of the MTC UE 711 at step 819. At thistime, the MTC MME 731 is retaining the MTC features supportable in thecorresponding radio network. When accepting the attachment of the MTC UE711, the MTC MME 731 notifies the MTC UE 111 of the supported MTCfeatures. Here, the MTC MME 731 expresses the supported MTC features ina bitmap for notifying of the MTC features and transmits the bitmap tothe MTC UE 711.

If the MME 730 accepts the attachment, the MTC UE 711 determines at step821 whether the MME 730 supports MTC. That is, the MTC UE 711 determineswhether the MME 730 is the MTC MME 731. At this time, the MTC UE 711 iscapable of determining whether the MME 730 is the MTC MME 731 accordingto whether the MTC features have been transmitted by the MME 730. If itis determined that the MTC features have been transmitted by the MME730, the MTC UE 711 determines that the MME 730 is the MTC MME 731.Otherwise, if it is determined that no MTC feature has been transmittedby the MME 730, the MTC UE 711 determines that the MME 730 is a normalMME.

The MTC UE 711 determines whether to use the supported MTC features ofthe MTC MME 731 at step 823. At this time, the MTC UE 711 determineswhether to use the supported MTC features according to the MTC policy.That is, the MTC UE 711 determines based on the MTC policy whether thesupported features include the essential feature. Here, if the supportedMTC features include the essential MTC feature, the MTC UE 711determines to use the supported MTC features. If the supported MTCfeatures do not include the essential MTC feature, the MTC UE 711determines whether to maintain the attachment to the MTC MME 731. Here,if it is determined to maintain the attachment, the MTC UE 711determines to use the supported MTC features. Otherwise, if it isdetermined not to maintain the attachment, the MTC UE 711 determines notto use the supported MTC features.

If it is determined to use the supported features at step 823, the MTCUE performs MTC via the MTC MME 731 at step 825. At this time, if thesupported MTC features include the essential MTC feature, the MTC UE 711is capable of performing the MTC using the essential MTC features. Here,the MTC UE 711 is capable of performing MTC using the MTC featureselected among the supported MTC features of the MTC MME 731 as well asthe essential MTC feature. If the supported MTC features do not includethe essential MTC feature, the MTC UE 711 is capable of performing MTCusing the supported MTC features of the MTC MME 731. Here, the MTC UE711 is capable of performing MTC with the MTC feature selected among thesupported MTC features of the MTC MME 731.

Otherwise, if it is determined not to use the supported MTC features atstep 823, the MTC UE 711 releases the attachment to the MTC MME 731 atstep 833.

Although the description is directed to an exemplary case where the MTCUE 711 determines whether the MTC features have been transmitted by theMME 730 to determine whether the MME 730 is the MTC MME 731 in thisembodiment, the present invention is not limited thereto. That is, thepresent invention can be implemented in such a way that the supportedMTC features are transmitted by the normal MME 733 as well as the MTCMME 731 and thus the MTC UE 711 differentiates between the MMEs. Thatis, the MTC MME 731 is retaining the supported MTC features while thenormal MME 733 is not retaining any supported MTC feature. If the MTC UE711 requests for attachment, the MTC MME 731 expresses the supported MTCfeatures in a bitmap for notifying of the MTC features and transmits thebitmap to the MTC UE 711. Meanwhile, if the MTC UE 711 request forattachment, the normal MME 733 expresses the supported MTC features in abitmap for notifying of the MTC features and transmits the bitmap to theMTC UE 711. Here, the bitmap is configured to indicate that the normalMME 733 has no supported MTC feature.

In this way, the MTC UE 711 is capable of checking whether the MME 730supports MTC. The MTC UE 711 is also capable of checking whether the MME730 supports the essential MTC feature or the selected MTC feature. Thatis, the MTC UE 711 is capable of discriminating between the MTC featuressupported and not supported by the MME 730.

FIG. 10 is a flowchart illustrating the operating procedure of the MMEin FIG. 9. In this embodiment, the description is made under theassumption that the MME is the MTC MME. In the case that the MME is anormal MME, the operating procedure of the normal MME is similar to thatof the previous embodiment, the detailed description thereon is omittedherein.

Referring to FIG. 10, in the operations procedure of the MME 730according to this embodiment, the MTC MME 731 first detects the attachrequest of the MTC UE 711 at step 911. At this time, the MTC MME 731checks the subscription identity information of the MTC UE 711. Next,the MTC MME 731 requests the HSS 740 for the subscription information ofthe MTC UE 711 at step 913. At this time, the MTC MME 731 reports thelocation of the MTC UE 711 to the HSS 740 to request for thesubscription information of the MTC UE 711. Here, the MTC MME 731transmits the subscription information of the MTC UE 711 to the HSS 740.

Subsequently, if the subscription information of the MTC UE 711 isreceived from the HSS 740, the MTC MME 731 detects this at step 915 andaccepts the attachment of the MTC UE 711 at step 917. At this time, theMTC MME 731 notifies the MTC UE 711 of the supported MTC features. Here,the MTC MME 131 expresses the supported MTC features in a bitmap fornotifying of the MTC features and transmits the bitmap to the MTC UE711. Afterward, the MTC MME 731 determines whether the attachment of theMTC UE 711 has been released at step 919. At this time, if the MTC UErequests for detachment, the MTC MME 731 detects this and accepts therelease of the detachment.

Finally, if no request for detachment is detected at step 919, the MTCMME 731 performs MTC with the MTC UE 711 at step 921. At this time, ifthe supported MTC features include the essential MTC feature, the MTCMME 731 is capable of performing MTC using the essential MTC feature ofthe MTC UE 711. In order to optimize MTC, the MTC MME 731 is capable ofchecking the selected MTC feature for the MTC UE 711 among the supportedMTC features. The MTC MME 731 is capable of performing MTC with thesupported MTC features for the MTC UE 711. Here, in order to optimizeMTC, the MTC MME 731 is capable of checking the selected MTC feature forthe MTC UE 711 among the supported MTC features.

FIG. 11 is a flowchart illustrating the operating procedure of the UE inFIG. 9. In this embodiment, the description is made under the assumptionthat the UE is the MTC UE.

Referring to FIG. 11, in the operating procedure of the UE 110 accordingto this embodiment, the MTC UE 711 first configures an MTC policyaccording to the command of the policy server 700 at step 1001. Here,the MTC policy includes the essential MTC features of the MTC UE 711,selected MTC feature, and information on whether it is possible tomaintain the attachment to the radio network which does not support theessential MTC feature. Afterward, the MTC UE 711 selects the MME 130 atstep 1003. That is, the MTC UE 711 selects one of the radio networksaccessible via the eNB 720 to access the MME 730. At this time, the MTCUE 711 is retaining the operator's informations of the radio networksaccessible via the eNB 720. Next, the MTC UE 711 requests the MME 730for attachment at step 1005. At this time, the MTC UE 711 is capable ofrequesting the MTC MME 731 or the normal MME for attachment. The MTC UE711 is also capable of transmitting the unique subscription identityinformation to the MME 730.

Subsequently, if the MME 730 accepts the attachment, the MTC UE 711detects this at step 1007 and determines whether the MME 730 supportsMTC at step 1009. At this time, the MTC UE 711 is capable of determiningwhether the MME 730 is the MTC MME 731 by checking whether the MME 730has transmitted the MTC features. If the MTC features have beentransmitted, the MTC UE 711 determines that the MME 730 is the MTC MME731. Otherwise, no MTC feature has been transmitted, the MTC UE 711determines that the MME 730 is a normal MME. The MTC UE 711 receives thebitmap indicating the MTC features from the MME 730 and checks thesupported MTC features of the MME 730. The MTC UE 711 is capable ofdetermining whether the MME 730 supports MTC for the MTC UE 711according to the supported features of the MME 730.

Subsequently, if it is determined that the MME 730 supports MTC at step1009, the MTC UE 711 determines whether to use the supported MTCfeatures of the MTC MME 731 at step 1011. At this time, the MTC UE 711is capable of determining whether to use the supported MTC featuresaccording to the MTC policy. Here, if the supported MTC features includethe essential MTC feature, the MTC UE 711 determines to use thesupported MTC features. If the supported MTC features do not include theessential MTC feature, the MTC UE 711 determines whether to maintain theattachment to the MTC MME 731 according to the MTC policy. Here, if itis determined to maintain the attachment, the MTC UE 711 determines touse the supported MTC features. If it is determined not to maintain theattachment, the MTC UE 711 determines not to use the supported MTCfeatures.

Finally, if it is determined to use the supported MTC features at step1011, the MTC UE 711 performs MTC through the MME 730, i.e. MTC MME 731,at step 1013. At this time, if the supported MTC features include theessential MTC feature, the MTC UE 711 is capable of performing MTC usingthe essential MTC features. The MTC UE 711 is also capable of performingMTC using the MTC feature selected among the supported MTC features ofthe MTC MME 731 in addition to the essential MTC features. If thesupported MTC features do not include any essential feature, the MTC UE711 is capable of performing MTC using the supported MTC features of theMTC MME 731. Here, the MTC UE 711 is capable of checking the MTC featureselected among the supported MTC features of the MTC MME 731 and usingthe selected MTC feature.

If it is determined not to support MTC at step 1009 or if it isdetermined not to use the supported MTC features, the MTC UE 711releases the attachment to the MME 730 at step 1021. At this time, theMTC UE 711 is capable of retaining the operator information of the radionetwork corresponding to the MME 730 to reference for selecting MME 730afterward. That is, the MTC UE 711 is capable of storing thecorresponding radio network operator information as selection forbiddeninformation so as not to request for attachment to the corresponding MME730.

If the MME 730 does not accept the attachment at step 1007 and if theMME 730 rejects the attachment, the MTC UE 711 detects this at step 1037and waits for the attachment retrial period at step 1039. At this time,the MTC UE 711 is capable of waiting for a predetermined attachmentretrial period. The MTC UE 711 is also capable of waiting for theattachment retrial period notified by the MME 730. Afterward, the MTC UE711 reselects the MME at step 1041 and returns the procedure to step1005. Next, the MTC UE 711 performs at least a part of steps 1005 to1041 again.

At this time, the MTC UE 711 is capable of storing the operatorinformations of the radio networks accessible via the eNB 720 and usingthe operator informations for selecting another MME 730. The MTC UE 711is also capable of using the other radio networks operators informationsnotified by the MTC MME 731 to select another MME 730. For example, ifthe operator informations of the respective radio networks are storedpreviously, the MTC UE 711 is capable of selecting another MME 730 usingthese informations and, otherwise, selecting another MME 730 as notifiedby the MTC MME 731. Here, the MTC UE 711 is capable of selecting anotherMME 730 by referencing the previously stored selection forbiddeninformation. That is, the MTC UE is capable of ruling out the selectionforbidden information in the operator informations of the respectiveradio networks that are stored previously or notified by the MTC MME 731selecting another MME 730 in selecting another MME 730.

According to this embodiment, it is possible to connect the UE 710 to anMME 730 supporting the corresponding supplementary function efficientlyin the wireless communication system. That is, the present invention iscapable of connecting the MTC UE 711 to the MTC MME 731 supporting thecorresponding essential MTC feature efficiently. As a consequence, theMTC MME 731 is capable of supporting MTC more efficiently and the MTC UE711 is capable of performing MTC more efficiently in the wirelesscommunication system.

Although exemplary embodiments of the present invention have beendescribed in detail hereinabove with specific terminology, this is forthe purpose of describing particular embodiments only and not intendedto be limiting of the invention. While particular embodiments of thepresent invention have been illustrated and described, it would beobvious to those skilled in the art that various other changes andmodifications can be made without departing from the spirit and scope ofthe invention.

What is claimed is:
 1. A method for connecting a data-centric terminalto a mobility management entity in a wireless communication system,comprising: requesting, at the data-centric terminal, the mobilitymanagement entity for attachment; and checking, when the mobilitymanagement entity responds, data-centric features supported by themobility management entity.
 2. The method of claim 1, furthercomprising: determining, when the mobility management entity accepts theattachment, whether the data-centric terminal is to maintain theattachment to the mobility management entity according to thedata-centric features; and performing, when the data-centric terminaldetermines to maintain the attachment, data-centric communication withthe mobility management entity using the data-centric feature and, whennot maintain the attachment, releasing the attachment to the mobilitymanagement entity.
 3. The method of claim 2, further comprisingtransmitting, at the mobility management entity when the data-centricterminal requests for attachment, a bitmap configured to indicate thedata-centric features to the data-centric terminal.
 4. The method ofclaim 1, further comprising checking, when the data-centric terminalrequests for attachment, the data-centric features for the data-centricterminal through subscription information of the data-centric terminalwhich the mobility management entity has registered with a homesubscriber server previously.
 5. The method of claim 2, furthercomprising accepting, at the mobility management entity, the attachmentof the data-centric terminal.
 6. The method of claim 2, furthercomprising: waiting, at the data-centric terminal when the mobilitymanagement entity rejects attachment of the data-centric terminal, for aperiod; and selecting, at the data-centric terminal, another mobilitymanagement entity to request for attachment after expiry of the period.7. A wireless communication system comprising: a data-centric terminalfor performing data-centric communication using a unique data-centricfeature; and a mobility management entity for managing mobility of thedata-centric terminal, wherein the mobility management entity notifies,when the data-centric terminal requests for attachment, the data-centricterminal of data-centric features supported by the mobility managemententity.
 8. The wireless communication system of claim 8, wherein thedata-centric terminal determines, when the mobility management entityaccepts the attachment, whether to maintain the attachment to themobility management entity according to the data-centric feature andperforms, when the data-centric terminals determines to maintain theattachment, data-centric communication with the mobility managemententity using the data-centric feature and, otherwise, releases theattachment to the mobility management entity.
 9. The wirelesscommunication system of claim 8, wherein the mobility management entityconfigures, when the data-centric terminal requests attachment, a bitmapindicating the data-centric features and transmits the bitmap to thedata-centric terminal.
 10. The wireless communication system of claim 7,further comprising a home subscriber server which retains subscriptioninformation including data-centric features for the data-centricterminal and provides the mobility management entity with thesubscription information of the data-centric information.
 11. Thewireless communication system of claim 8, wherein the mobilitymanagement entity accepts, when the data-centric terminal requests forattachment, the attachment of the data-centric terminal.
 12. Thewireless communication system of claim 8, wherein the data-centricterminal waits, when the mobility management entity rejects theattachment, for a period and selects, when the period expires, anothermobility management entity to request for attachment.